Acute and chronic diseases, such as diabetes and psoriasis, or acute injuries result in a severe damage to the skin. This damage may involve the entire thickness of the skin and may often include deeper tissues wherein the depth of the damage varies over the entire damaged zone. The damaged skin loses the anatomic organization of a healthy skin as the stratum corneum is at least partially destroyed and consequently the inner layers of the skin are no longer protected from the external environment. Moreover, the damaged skin typically contains dead eschar, diseased and/or abnormal cells that must be removed in order to enable healing. Leaving the dead eschar in place extends and deepens the damage into the neighboring, undamaged tissues. This dead eschar also serves as a medium for bacteria growth, and a source of infection, contamination and sepsis which may be life threatening.
Removal of the dead eschar, diseased and/or abnormal cells, also known as “debridement”, is executed either by surgical procedures or by using enzymatic means. Surgery is one of the most common procedures of debridement wherein small necrotic areas are excised of the entire damaged skin. This method is limited to small non-tangential surfaces. It also involves the removal of large fractions of healthy tissue which, if preserved, could serve as a source for the natural healing processes. Surgical procedures are also long, expensive and require complicated medical resources.
U.S. Pat. No. 3,910,266 describes a method and apparatus that provide a jet of pressurized fluids which is used for penetrating the skin and inserting cosmetic or therapeutic agents into the skin. U.S. Pat. No. 5,697,920 describes means for mechanic debriding using a jet of pressurized fluids and a brush. U.S. Pat. Nos. 5,941,859; 5,989,211 and 6,264,666 describe medical instruments for supplying to and removing rinsing fluids from the skin. A hand-held surgical apparatus adapted to be used substantially as a sharp surgical tool for removal of diseased tissue by utilizing pressurized fluid jets, is described in U.S. Pat. Nos. 5,037,431. 5,358,494 describes an irrigation dressing comprising a conduit for supplying the irrigation fluids and pad attached at the tip of the conduit wherein the pad is adapted to fill the wound cavity, thereby supporting the walls of the wound. However, the methods and apparatus described in the above patents are not adapted for providing a sealed system that occludes a defined treatment zone. Furthermore, these methods and apparatus cannot provide a sealed environment that encompasses the wound and that is resistant to pressure accumulated therein.
U.S. Pat. No. 4,969,881 describes a hyperbaric oxygen dressing adapted for treating body sores with a flow of oxygen by supplying oxygen through a suitable feed tube dressing utilizing a gas releasing system. The dressing described in this patent is not suitable for draining secretions or excess therapeutic materials from the wound area and/or for providing a flow of therapeutic solution to the wound area.
U.S. Patent Application, Publication No. 2003/0050594, describes a wound therapy system adapted for treating a wound with a gradient of various mechanical forces, particularly vacuum, the system comprising transfer assembly, collecting assembly and a source for establishing said gradient, specifically a pump, connected to the transfer assembly. U.S. Patent Application, Publication No. 2003/0225441, describes a device for applying thermotherapeutic liquids to a selected area of a patient, the device comprising an applicator for maintaining liquids at a desired temperature, the applicator being held about the selected area through negative pressure generated by a pump connected thereto.
U.S. Pat. No. 6,135,116 describes a method for wound therapy, comprising providing pneumatic compression therapy and vacuum assisted closure therapy, concurrently. U.S. Pat. No. 6,767,334 describes a wound treatment device adapted to provide a positive pressure to a wound site, the device comprises a pad for inserting into the wound, a pump and a fluid conduit for conveying fluids through the pad to the wound, a venturi communication to create suction at the pad and within the wound cavity and a reservoir for collecting the fluid from the wound
U.S. Pat. Nos. 1,385,346; 6,398,767; 6,458,109 and EP 1014905 describe dressings which are secured to the skin surface around a wound. Each dressing includes a single infusion tube and a single drainage tube having a fixed position with respect to the wound surface. International Patent Application, Publication No. WO 03/01136, assigned to the common assignees of the present invention, describes a device for the removal of cells from a viable tissue. The device includes an inlet tube adapted for applying a stream of enzymatic solutions over and onto the tissue and an outlet tube for removing excess fluids and debris. The distance between the opening of the outlet tube and the skin may be adjusted by a screw mechanism. Each one of the dressing and devices described in the aforementioned inventions include a single infusion (inlet) tube having a fixed position with respect to the wound. Thus, these dressing and devices cannot be adjusted to penetrate deeply into the lesion and are unsuitable for infusing areas that are not readily accessible.
A paper by the inventor of the present invention published after the priority date of the present application describes applying a stream of active proteolytic enzyme for a few hours to provide an effective debridement (Freeman et al., Wound 16:201-205, June 2004). The streaming of a buffer solution devoid of enzymes was found to be ineffective. Furthermore, treatment with static enzyme solution for a similar time period had no effect and visual change was not observed.
Enzymatic debridement is advantageous over mechanical and surgical debridement mainly since it is less painful and does not involve the loss of a great deal of blood. The application of proteolytic enzymes for debridement is well known in the art (G. Rodeheaver, 1975, Am. J. Surg. 129(5):537-544). These enzymes include those generally found in to plant sources, such as papaya (papain), fig (ficin), and pineapple (bromelain). Hydrolytic enzymes derived from the pineapple plant that are useful for digestion, dissection and separation of non-viable, especially eschar tissue, from viable tissue in a mammalian host are described in U.S. Pat. Nos. 4,197,291; 4,226,854; 4,307,081; 4,329,430 and 5,830,739 among others. U.S. Pat. No. 6,017,531 describes a proteolytic composition which includes an extracellular neutral protease produced by Vibrio proteolyticus. 
The degree of therapeutic activity obtained from topical application of proteolytic enzymes is governed, inter alia, by the intrinsic catalytic characteristics of those enzymes. The major problems associated with topical use of compositions comprising proteolytic enzymes are that the catalytic activity of the enzymes rapidly attenuates due to the typical low pH at the lesion area, adsorption of enzyme molecules to the surface of the wound bed and/or the surface of the dressing thus preventing their accessibility to other regions at the wound bed and inhibition of enzymatic activity by moieties within the wound exudates. Accordingly, obtaining stable enzymatic formulations is often complicated.